ORICA argued against a proposal to measure mercury levels near its Port Botany chemical plant, partly because it worried emissions from sources including fish and broken thermometers might skew the results, documents show.

A Fairfax Media investigation revealed that high concentrations of mercury were found in an estuary near Orica's former ChlorAlkali plant, which operated between 1945 and 2002 using mercury cell technology.

Past reports commissioned by the company have ignored the issue of soil contamination around its plant - an area potentially encompassing more than 1000 homes.

A group of residents commissioned Hg Recoveries, a member of the United Nations Environment Program Global Mercury Partnership, to develop, pro bono, a proposal for studying mercury levels in a 1.25-kilometre area around the Botany plant at a cost of $400,000.

Advertisement

They put the proposal to a December 11 meeting of the community liaison committee, a body that mediates between Orica and residents.

Orica opposed the study and its presentation raised concerns that emissions from sources including a nearby power station and dental fillings would not be differentiated in the study's results.

The managing director of Hg Recoveries, Andrew Helps, said these contributions were comparatively minimal.

''They were basically inferring the residents have a ritual when they get home at night to smash thermometers,'' he said. ''I think they know what's out there, they just don't want everyone else to know.''

Mr Helps estimated the mercury emitted by the nearby Bunnerong Power Station was equal to two months' worth from Orica's plant, while that from broken thermometers was equal to 20 seconds' worth.

A spokesman for Orica said they simply wanted all sources of mercury accounted for.

''They [were] not raised to in any way … distract from Orica's commitment to remediating mercury,'' he said.

He said Orica opposed the proposal because it was inaccurate and not supported by qualifications or raised through proper channels.

Orica declined to say what advice this assessment was based on.

Dr Mariann Lloyd-Smith, a lawyer specialising in chemicals policy and a member of the community advocacy group the National Toxics Network, said Hg Recoveries was among Australia's leading mercury experts.

The company was recently given a permit by the federal Environment Department to extract ambient mercury in Victoria.

Some residents at the meeting supported a study but said it should not be paid for by Orica.

Orica said it would consider paying for independent testing and that it was seeking government advice on testing methods.

Resident Chantal Snell, who lives about one kilometre away from the plant and requested the study, said Orica was dismissive. ''It looked like they just wanted to duck [it],'' she said.

The Greens said Orica's opposition was further evidence the government needed to compel them to conduct a study.

''Orica's ridiculous broken thermometer and tooth filling defence should be a red flag to the Environment Minister, Robyn Parker,'' said MLC Cate Faehrmann. ''The minister has to step in.''